diff mbox

[2/6] mmc_block: Allow more than 8 partitions per card

Message ID 1303520502-32171-3-git-send-email-john.stultz@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

John Stultz April 23, 2011, 1:01 a.m. UTC 
From: Colin Cross <ccross@android.com>

Set the GENHD_FL_EXT_DEVT flag, which will allocate minor numbers
in major 259 for partitions past disk->minors.

Also remove the use of disk_devt to determine devidx from md->disk.
md->disk->first_minor is always initialized from devidx and can
always be used to recover it.

CC: Chris Ball <cjb@laptop.org>
CC: Arnd Bergmann <arnd@arndb.de>
CC: Dima Zavin <dima@android.com>
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 drivers/mmc/card/block.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

Comments

Arnd Bergmann April 26, 2011, 1:22 p.m. UTC | #1 
On Saturday 23 April 2011, John Stultz wrote:
> From: Colin Cross <ccross@android.com>
> 
> Set the GENHD_FL_EXT_DEVT flag, which will allocate minor numbers
> in major 259 for partitions past disk->minors.
> 
> Also remove the use of disk_devt to determine devidx from md->disk.
> md->disk->first_minor is always initialized from devidx and can
> always be used to recover it.
> 
> CC: Chris Ball <cjb@laptop.org>
> CC: Arnd Bergmann <arnd@arndb.de>
> CC: Dima Zavin <dima@android.com>
> Signed-off-by: Colin Cross <ccross@android.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>

The new code looks reasonable, but wouldn't changing this be incompatible
with existing root file systems that contain static device nodes?

	Arnd
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Colin Cross April 26, 2011, 4:10 p.m. UTC | #2 
On Tue, Apr 26, 2011 at 6:22 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> On Saturday 23 April 2011, John Stultz wrote:
>> From: Colin Cross <ccross@android.com>
>>
>> Set the GENHD_FL_EXT_DEVT flag, which will allocate minor numbers
>> in major 259 for partitions past disk->minors.
>>
>> Also remove the use of disk_devt to determine devidx from md->disk.
>> md->disk->first_minor is always initialized from devidx and can
>> always be used to recover it.
>>
>> CC: Chris Ball <cjb@laptop.org>
>> CC: Arnd Bergmann <arnd@arndb.de>
>> CC: Dima Zavin <dima@android.com>
>> Signed-off-by: Colin Cross <ccross@android.com>
>> Signed-off-by: John Stultz <john.stultz@linaro.org>
>
> The new code looks reasonable, but wouldn't changing this be incompatible
> with existing root file systems that contain static device nodes?

I don't think so.  Without this change, /dev/mmcblk0p1 will be (179,
1), /dev/mmcblk0p7 will be (179, 7), and /dev/mmcblk0p8 will be
dropped.  After this change, /dev/mmcblk0p1-7 will be the same, but
/dev/mmcblk0p8 will be (259, <random number>).  A root file system
with static inodes will still have access to partitions 1-7, and will
still not have access to dynamically-assigned partition 8.
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Arnd Bergmann April 26, 2011, 4:13 p.m. UTC | #3 
On Tuesday 26 April 2011, Colin Cross wrote:
> On Tue, Apr 26, 2011 at 6:22 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > On Saturday 23 April 2011, John Stultz wrote:
> >> From: Colin Cross <ccross@android.com>
> >>
> >> Set the GENHD_FL_EXT_DEVT flag, which will allocate minor numbers
> >> in major 259 for partitions past disk->minors.
> >>
> >> Also remove the use of disk_devt to determine devidx from md->disk.
> >> md->disk->first_minor is always initialized from devidx and can
> >> always be used to recover it.
> >>
> >> CC: Chris Ball <cjb@laptop.org>
> >> CC: Arnd Bergmann <arnd@arndb.de>
> >> CC: Dima Zavin <dima@android.com>
> >> Signed-off-by: Colin Cross <ccross@android.com>
> >> Signed-off-by: John Stultz <john.stultz@linaro.org>
> >
> > The new code looks reasonable, but wouldn't changing this be incompatible
> > with existing root file systems that contain static device nodes?
> 
> I don't think so.  Without this change, /dev/mmcblk0p1 will be (179,
> 1), /dev/mmcblk0p7 will be (179, 7), and /dev/mmcblk0p8 will be
> dropped.  After this change, /dev/mmcblk0p1-7 will be the same, but
> /dev/mmcblk0p8 will be (259, <random number>).  A root file system
> with static inodes will still have access to partitions 1-7, and will
> still not have access to dynamically-assigned partition 8.

Ah, I see.

The patch looks good to me then.

	Arnd
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diff mbox

Patch

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index edac9ac..f69f948 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -102,11 +102,7 @@  static void mmc_blk_put(struct mmc_blk_data *md)
 	mutex_lock(&open_lock);
 	md->usage--;
 	if (md->usage == 0) {
-		int devmaj = MAJOR(disk_devt(md->disk));
-		int devidx = MINOR(disk_devt(md->disk)) / perdev_minors;
-
-		if (!devmaj)
-			devidx = md->disk->first_minor / perdev_minors;
+		int devidx = md->disk->first_minor / perdev_minors;
 
 		blk_cleanup_queue(md->queue.queue);
 
@@ -623,6 +619,7 @@  static struct mmc_blk_data *mmc_blk_alloc(struct mmc_card *card)
 	md->disk->private_data = md;
 	md->disk->queue = md->queue.queue;
 	md->disk->driverfs_dev = &card->dev;
+	md->disk->flags = GENHD_FL_EXT_DEVT;
 	set_disk_ro(md->disk, md->read_only);
 
 	/*